In the formulation of cementitious compositions it is known in the art to use mixtures of different hydraulic cements, as well as other additives such as accelerators and retarders in order to provide such characteristics of setting times, strengths, and volume changes as are needed to meet the needs or demands of various specialty applications. Ready-to-use cement mixes are conventionally sold in relatively small packages for convenient use in carrying out small jobs such as in minor repair and patching applications or for the setting of fence posts and similar such endeavors. By way of example, various ready-to-use cement mixes are marketed under the designation "SAKRETE" or "QUIKRETE" and others, in sacks having a volume of about 0.6 cubic feet and weighing about 80 pounds per sack--providing a bulk density of about 135-150 pounds per cubic foot (ppcf). Typically, such ready-to-use mixes are sold as concrete mix containing relatively coarse aggregates, and thus suitable for setting fence posts or the repair of driveways or sidewalks or the like to a thickness of 2 inches or more, and sand mix in which the aggregate component is of a much smaller size suitable for patching with thicknesses less than 2 inches. Concrete mix and sand mix typically comprises a mixture of Type I portland cement, aggregate and sand. Another type of ready-to-use cement mix is mortar mix, which is useful in laying bricks or cement stepping stones or the like. Mortar mix normally is formed of masonry cement meeting ASTM (American Society for Testing Materials) Designation C 91-89, usually Type N cement, mixed with various aggregates to meet specifications called for in ASTM Designation C 387-87 or C 270-89.
Another type of cementitious composition which can be sold in ready-to-use packages is disclosed in U.S. Pat. No. 4,769,077 to Crocker. This patent discloses fast setting shrinkage compensating cementitious formulations for use in effecting grouting repairs in road surfaces and the like. These formulations comprise a hydraulic cement mixture of a major amount of a portland cement constituent and a minor mount of an expansive ettringite forming sulfoalumina cement constituent, along with an aggregate and an accelerator. The accelerator component is a polyvalent metal salt of formic acid, specifically an alkaline earth metal formate such as calcium formate. Specific formulations include mixtures of a Type I, Type IP, or Type III cement with a Type K, Type M, or Type S expansive cement with weight ratios within the range of 2:3. Where Type IP cement is used, it is present as a major cement constituent in relation to the expansive cement. A preferred mixture in the Crocker patent employs Type III high early strength cement and Type K expansive cement in a ratio of Type III to Type K of about 7:3. However, Type M and Type S expansive cements can also be used. These cements, which meet ASTM C 845-90 are not to be confused with masonry cements, as described earlier, meeting ASTM C 91-89. The cementitious composition can be used to effect a grouting repair by mixing the dry formulation with water to provide a cementitious slurry having relatively short initial and final Gillmore setting times, 7 and 16 minutes, respectively, and 1-7 days curing. Aggregates suitable for use in this formulation include those having an average particle size of less than 3/8 inch and meeting standards as set forth in ASTM C 33, ASTM C 144 and ASTM C 330. The latter as described in greater detail below is a lightweight aggregate.
The standards for lightweight aggregates suitable for use in structural concrete are set forth in ASTM C 330-89. Such aggregates intended for use in masonry units are set forth in ASTM C 331-89. Lightweight aggregates and lightweight concrete formulations made from such aggregates are described in "Lightweight Concrete", published by the Expanded Shale, Clay and Slate Institute, Washington, D.C., October 1971. As described there under the heading "What is a Lightweight Aggregate?", such aggregates can range from the so-called "super lightweights" which can be used in making concrete weighing 15 to 20 pounds per cubic foot to the natural aggregates and finally to the expanded shale, clay and slate aggregates which can produce structural concrete ranging from about 85 to 115 pounds per cubic foot when produced by the rotary kiln method and from about 90 to 120 pounds per cubic foot when produced by sintering. Structural lightweight concrete is described as having a 28 day compressive strength of at least 2,500 pounds per square inch and an air dry weight of no more than 115 pounds per cubic foot. Weights can be increased by replacing a portion of the lightweight aggregate with sand.
Lightweight aggregates in the use of cement formulations are disclosed in U.S. Pat. Nos. 3,600,476 to Suzuki et al., 3,661,604 to Artmann, 4,504,320 to Rizer et al. and 4,741,782 to Styron. The patent to Suzuki et al. discloses the manufacture of lightweight aggregates from fly ash and sludge, which can be mixed with portland cement and sand to form concrete blocks. The patent to Artmann discloses lightweight concrete having a density of 800-1,800 Kg/m.sup.3 (about 50 to 110 pounds per cubic foot) formed from portland cement and an aggregate mixture derived from clay, sand and crushed bricks. The Rizer et al. patent discloses a fiber reinforced cementitious product having a density of less than 85 pounds per cubic foot. Disclosed here is a mixture of Type III and Type I portland cements with an aggregate component including fly ash, silica fume and microspheres. The silica fume is said to appear to have pozzolanic properties. The aforementioned patent to Styron discloses a process for the formulation of lightweight aggregate pellets from fly ash, cement and silica fume dust.